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My CL175K7

Richard Pitman

Richard Pitman

Veteran Member
Joined
Jun 1, 2020
Total Posts
2,874
Total likes
1,112
Location
Worcester, England
Back in my youth, I had a brand new cherry CB175K6, my favourite bike of all time.

In 2014, I decided to revisit those happy days, and get a CB175 to restore. At the time, all I could find locally was an imported CL175K7. Naively, I thought it was more or less the same bike with a different exhaust.

So I bought it, and rebuilt it into my version of a CB175K6. David Silvers exhausts, rebuilt engine etc. Got it registered for the road.
 

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After a while, it began to nag me that it wasn't really correct, CL tank and seat were wrong for the CB style, so I bought a CB K6 tank and seat, painted and recovered them myself. Also correct handlebars and UK CB175 headlight etc.
 

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Time passed, and I bought a CB175K4, for which I'll start another thread.

It occurred to me that my bike still wasn't correct as a CB175K6, with that K7/CB200 front end and rear grab rail, CL rear fender and wheel rim. So, I put it back to CL175K7 configuration. Repainted the CL tank, had the pipes Cerakoted, built the wheels with stainless steel rims.

Along the way, this left me with quite a few parts left over, which is another story …
 

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More fun with the CL175.

I took it for a short ride yesterday, all seemed OK. This afternoon, after my dog walking and gardening duties, I went down to my garage, intending to check my SL175alike over. However, I soon noticed the reek of petrol ( gasoline ), and discovered that the best part of a gallon of Tesco Momentum 99 octane ( hopefully low ethanol content ) had leaked onto my concrete garage floor. The tube that links the two halves of the CL175 tank had perished and was dripping fuel. The tank was empty by now, but luckily the leak had been slow enough that the fuel had evaporated. Good job no one had struck a light !

Had to change my clothes, after complaints about my smell !

Oddly enough, I'd just been reading Allen Millyards column in Motor Cycle Mechanics, he'd had similar issue on his Kawa 6 build. So we'll both be looking for ethanol resistant fuel hose.

Here's my CL when it came back from yesterdays ride, shows the modded Speed Triple can.
 

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I haven't used the CL for a while, so I decided to go for a ride today.

Except, it would not start. I wasted half an hour, changing the plugs, swapping battery, checking that the advance mech hadn't stuck on full advance (Charlies ignition) no joy.

Fuel in tank, tap on reserve, so it couldn't be lack of petrol.

Just to rule that out, I slackened the float bowl drain screws. Dry as the proverbial. I always turn the fuel off when not in use, so I guess the contents of the float bowl had evaporated and the needle valves got gummed up. A few shakes and the fuel started to flow, then the engine started first try.

Just shows I should not jump to conclusions.
 
More CL175 fuel problems !

I've been for a few rides on it lately, without issue. However, yesterday I decided to take
it for a spin, in the extreme hot weather we are currently 'enjoying'. Turned the fuel on,
started the engine, and as I wheeled it out of the garage I noticed that I was leaving a trail
of fuel. Turned out that the left hand carb, the one you can't get at because of the CL exhaust,
was overflowing. I suspected a stuck float valve, but the usual remedy of a sharp tap on the
flaot bowl failed to stem the flow, so I turned off the fuel and put the CL175 away.


As I'd already got togged up in my riding gear, I took the 600 out for a spin instead. Riding it at 175
speeds, as I'd just got my 175 riding gear on, open face Bell helmet, lightweight gloves and boots,
all the vents in my textile jacket open. The Hornet engine is suprisingly tractable for a bike with
a 13k redline, and is happy to run easily at 4k rpm in 4th gear along the back lanes, in the 45-60mph
speed range. Got a dynojet kit fitted, and the fuelling is spot on, no flat spots, creamy from low
rpm right up to the limiter.Probably running a bit rich, but still returns 45mpg or better.


This afternoon, after watching the Brno Motogp race, I fixed the 175. My turn to say 'Why did Honda
build it like that ?', entire exhaust sytem has to come off before the left hand side carb, side panel and
air filter can be got at. Still, practice makes perfect, and in the space of an hour I'd got the job
done. Turned out that the float had sprung a leak, not something I've personally encountered before.
Spare float fitted, just returned from test ride, running fine. Still 'bloody hot', to quote James.
 
My CL175, rolled out ready for a ride later today.

qRaU1ba.jpg


I've refitted the original silencer can, with rust damage welded up a while ago, still holding up well, fresh coat of PJ1 exhaust paint, probably should have used VHT ! I used JB Weld High Heat epoxy putty for the pipe to muffler gasket.
Mods to this bike include aftermarket (Chinese) regulator rectifier, stainless steel wheel rims with K82 tyres. I have fitted a larger CB spec headlamp, with the UK lighting switch on the shell, along with a UK spec righthand switch gear. This deletes the ( unwanted by me ) kill switch and suicide (OFF-DIP-MAIN) light switch for a safer DIP-MAIN switch. CB600 mirrors and pattern handlebars.

Cerakoted exhaust headers. LED bulbs throughout, apart from the headlamp. I rarely go out on it at night, and don't use day time running lights.


The engine is my 'spare' one rebuilt from a ceased <sic> engine from a breaker. Fully stripped, kick start shaft replaced and 1.0mm overbore, otherwise all original parts reused. Charlies Place ignition. Valves lapped in.


The original engine is sitting in my SL175 test bed. This engine also has a replacement kick start shaft and a 1.0mm overbore, along with a CB200 oil pump, new cam chain and tensioner assembly, valves lapped, CB360 stator. Ready to fit if the above engine expires.


All three engines have their original clutches, plates and springs. Never experienced any problems with these.
 
Yakeye said:
Richard, beautiful bike!
Click to expand...
Thanks both !

However, as we know from buying stuff on the net, things always look better in photos than they do in the flesh, always a few areas that could be improved upon.

The JB Weld High Heat putty was a qualified success. On the plus side, it cured hard and stayed adherent to the pipes. On the minus side, I still have a bit of a leak between the lower pipe and the muffler. Makes itself known with popping and banging on the over run, amusing at first but irritating after a while. I'll bung some more JB onto the joint when I get a round tooit.

Had a nice ride, exploring the local back roads. I've lived in this area for 50+ years, and I'm still finding country lanes within a 15 mile radius from home that I've never been down before. The CL is the ideal bike for this, happily pottering along at 30mph or less in the lanes, high bars give good visibility for looking over hedges. Easily keeps up with A road traffic on the ride home but does get stuck behind cars dawdling at 50-55mph,not enough poke for a safe overtake.
 
So, I bought a mint CL175 exhaust off Ebay. After removing my existing system, I discovered that the new system wouldn't fit, because it came off a CL175 sloper, not stated in the advert.

Rather than put the old system back on straight away, I decided to fit my spare set of David Silvers pipes, partly because I'm about to swap the carbs out, ease of access.

Went for a ride this afternoon, and it runs better with these pipes. Hate to say this, but I think it looks better, too.

Pictured here by the Croome Court park folly, on Dunstall Common. Always make me smile, remembering a club members 500/4 back in the day, with a (Paul) Dunstall exhaust.

z6ZgENV.jpg


aCC1oj0.jpg
 
Wife and I are NT members, and we ascended the tower on an open day, back in November 2013.

View from the top with the snow capped Malvern Hills in the distance.

affQnAm.jpg
 
Nothing better than the UK's National Trust!
Croome is a great place, been a while since we last went.

Bike looks good Richard, hope to trial ride mine before winter creeps in and make something of 2020.
 
Richard Pitman said:
Thanks. All done on my mobile phone. I gave up on using a 'proper' camera some years back, apart from lack of zoom the phone does all that I need. It's only a Samsung Note4, nothing cutting edge.
Click to expand...

I'm doing the same thing Richard, all my pictures are from my Galaxy S5 which is now going on 7 years old and still works marvelously (and has a replaceable battery too, unlike most of the later versions, and I'm still on the original battery)
 
The CL175 has been running OK, apart from a very unsteady idle.


So today I fitted a spare set of previously cleaned carbs, set up to CB175 spec as per that document I
posted the other day.


98 mains, 38 pilots, needles in third (middle) slot, mixture screws 1 1/4 turns out. I also fitted the
new float valves that arrived a few days ago. These are marked 1.5, as opposed to the ones fitted, which
are marked 1.7, and do have a slightly larger bore than the 1.5 parts. Hopefully this won't cause an issue
when running flat out. Float heights set as close as I could get them to 21mm, using a float level gauge,
checked again with my calipers.


While the air filters were off, I set the throttle stop screws so that they were (more or less) identical
on each side, looking down the venturi with a flashlight (aka a torch in UK speak ).

Fuel, choke and ignition on, started first go, and once warm idled nicely once the throttle stops were set.
Responds crisply to the throttle. No leaks, I actually think I've got it right this time. No time for test
ride before the rain set in.
 
Well, serves me right for over confidence in my abilities.


Test ride this afternoon, engine started first go, rode smoothly away.


But once out on the open road, it didn't like full throttle, after 6k rpm it was surging and
missing, felt like fuel starvation. So I decided those 1.5 float valves were the problem.
Got back home, took out right hand plug, light tan colour, obviously running lean I thought,
confirming my theory.


But then I took out the left hand plug, thick black soot. And then I noticed the pool of fuel from
the left hand carb overflow tube. Why ??? I've just fitted a brand new (1.5) float valve assembly,
checked the float for leaks, set the float height and reassembled, ensuring that the float moved freely.
So I fitted the 1.7 float valve and float from the carb I'd just swapped out, overflow problem cured.

Off out for another test ride, much better but still hesitating at full throttle.Ticks over smoothly and reliably
now at 1200 rpm, runs nicely to 6k rpm or so. So I'm now suspecting that it's the 1.5 float valve in the
other carb that is the remaining problem, and I'll swap that for the parts from the other swapped carb.


I may also fit my K4 air filters, as this full throttle hesitancy also feels a bit like same issue on my
CB175, obstructed air flow in the K6/CB200 air boxes. On this bike, with the CL exhaust, I was running
92 mains, I've now fitted 98 mains to match the CB175 exhausts.
 
Changed the parts mentioned above, no time for test ride today, but it starts instantly and runs nicely, so fingers crossed.

I wanted a CB175 side panel, to replace the left hand CL side panel.

A quick look Ebay found this optimist:

https://www.ebay.co.uk/itm/HONDA-CB175-LEFT-HAND-SIDE-PANEL-IN-GOOD-CONDITION/133553807072?hash=item1f186d5ee0:g:HgUAAOSwe~JfdiK7

He also has a right hand panel and badge for 200 quid !!!!

I've just taken delivery of a brand new left hand panel in red from David Silver, 28 quid + vat and delivery. Still wrapped in Honda paper and sealed in a Honda plastic bag, perfect.

https://www.davidsilverspares.co.uk/CB175K6-SUPER-SPORT-1972/part_336062/
 
Don't you just love old carburettors !

I've gone from a bike that ran fine at full throttle, but was hard to start, with a poor /non existant idle, to one that starts on the button, idles beautifully at 1200 rpm when warm, responds nicely to the throttle. Then falls flat on its face at full throttle, or past 7K rpm reached at part throttle.

Fine around town, or poodling around at 50mph, useless on the open road.

It's not the air filters, I've tried both K4 and K6 variants. Plugs are both a nice tan colour.

I'm going to have another go at the float levels, also try the 92 mains with needle in slot 4, as CL spec. Cleaned another pair of carb bodies last night in the u/s tank, but I don't think this is dirt related given the nice idle and easy starting, feels more like fuel starvation to me
 
Side panels are a nightmare on the CB's with twin side exhausts.
The rh sides are esp rare, so £££££££, I paid £125 less badge but nos a few months back.
LH sides are easy to buy, mine from DS too.

My gaskets are here from DS, all real Honda, awaiting the coil tomorrow. Will then see if all is well.
Carbs drive me mad, electrics a close second.

Good luck!
 
Out of 3 175's that I've owned, I was only able to get one running well on the stock carbs, the other 2 only ran properly after putting the Wincycles aftermarket carbs on them. I now have 2 spare sets of stock carbs that I cannot get to run right.
 
Middletons said:
Out of 3 175's that I've owned, I was only able to get one running well on the stock carbs, the other 2 only ran properly after putting the Wincycles aftermarket carbs on them. I now have 2 spare sets of stock carbs that I cannot get to run right.
Click to expand...

If I move forward with my rebuild, I may be in the market for aftermarket carbs. What are the recommended aftermarket carbs for the CL175K6?
 
Not available over here, cost as much again to import from the US.

I vaguely wondered about the cheap Mikuni VM22 clones on Ebay, they appear to have the correct 48mm spacing at the inlet manifold side.

Or these even cheaper PZ things, although I don't like the choke butterfly, prefer the Mikuni enrichment device.

Both described as 26mm, but more likely 20 - 22mm in the main ventur1.
 
Back on topic. Swapped the carbs again, floats set, 38 pilots, 92 mains, needle in 4 from top.

Starts easily, idles OKish, not as nice as yesterdays set, still hits the wall past 7k rpm / WOT. Half closing the choke at that point does cause the rpms to increase a bit, then drop when choke is closed. 60 mph today.

So the next experiment is larger main jets, 98 upwards. I have a range of jets for my Hornet, up to 108. These have the same external dimensions as the 175 parts.
 
Some progress.

I fitted some 102 mains, left over from my Hornet. It now pulls full throttle without the hesitation from 7k onwards, and was doing 65-70mph in this afternoons blustery weather.

So now, it starts well, idles reasonably and is OK at full throttle. It's now not happy in the mid range, so tomorrows experiment is to put the needles back into the middle (3rd) notch, dropping them down from the 4th notch, hopefully to lean out the midrange. I could also try the 98 mains.
 
Middletons said:
Interesting that you you are ending up that large on the mains. Seems like you are on the right track though!
Click to expand...

It's probably too large, but I thought I'd go to the other extreme first, to see if it made a difference that I could notice. I think it shows that it's the jetting that is at issue, rather than something unrelated like ignition or valve clearances.
 
Running with the 102 mains and needle in 3rd slot. Still runs to redline in the gears, but midrange still doesn't feel quite right. Pulled the plugs and they are black, obviously too rich. So I put the 98 mains back in, and the problem returned, hits the wall at 7k rpm. When this happens, half closing the choke allows it to rev on to 9k or so, obviously too lean now, confirmed by plugs which are now returning to a tan colour after being black and sooty.

I can't believe that going up or down 4 increments on the mains would make such a difference.

Clutching at straws now. I swapped the jets complete with jet holder ( emulsion tube ?), as it's easier to change jets on the bench, then refit entire assembly back into carb on the bike. I'm now wondering if wear in that part might be an issue, so next experiment is the 98 jets mounted in the jet holders that previously worked with the 102 mains.
 
Maybe the needle and the needle jet(?) on these carbs get worn really easily, and that accounts for their strange behavior. Maybe the vibrations?
 
Please pardon my total dumb guy response, but if 102 mains are "too rich" and 98 mains are "too lean" (at least in some areas of the power band), could you give 100 mains a try?

-Goldy Locks-
 
Rickhoutx said:
Please pardon my total dumb guy response, but if 102 mains are "too rich" and 98 mains are "too lean" (at least in some areas of the power band), could you give 100 mains a try?

-Goldy Locks-
Click to expand...

Not a dumb guy response, it's obviously a good idea. It is possible either he doesn't have any or can't find them, but he is right in wondering how such a small change can make such a large difference, I'm surprised by it myself. Though the 175 engine is obviously smaller per cylinder, I made incremental changes of 5 and 10 in jets for my 450 and sometimes felt and saw very little difference. I think Middletons may be onto something with the needle jet and needle match, either they're different or possibly worn but the latter is probably less likely.
 
However, IF you do the math, the 102 (actually 102.5) jetting flows 10.5% more volume than the 98 (actually 97.5) jet ........

A 10+% increase in fuel volume to the mixture IS significant.......

Remember, we are seeking a WEIGHT of air over WEIGHT of fuel ratio, and proportionally, the fuel is much heavier per unit of volume....(~560 times as dense).........

THIS is yet another reason why a "small" drilling inaccuracy in aftermarket carb kit jets produces such profound performance errors.......

I can go into this deeper if requested.....
 
Last edited:
Thanks for that, food for thought.

I put the 98 mains back in, on a different set of jet holders, went for a test ride, same as before. Ok to 7k rpm, then bogs down at full throttle, opening the choke to around halfway at this point causes the revs to increase, able to go to 9k then.

I took the air filters off when I got home, to check the choke operation, really was half choke, ventur1 almost half occluded by choke flap.

Two further things to try. Needles back into slot 4.

I'm uncertain about the provenance of my 98 jets, wondering now if they came from a 'Rusty Riders' rebuild kit. I have ordered some allegedly Keihin 98 jets off Ebay, see if they alter things.
 
The real deal keihin’s will have the logo.

i need to get a few 175 jets myself. I’m pretty sure jetsrus has that style, but I need to confirm. I know that doesn’t help folks out of the US...
 
Todays instalment.

I have introduced too many variables.

Needles in 4th slot from top, 98 main jets as above. However, as I'd removed the K4 airfilters, to check the choke operation, I decided to refit a pair of later K7/CB200 filters, which have as standard the baffling, which I removed from another pair on my CB175.

Result - bike now starts first go, and idles reasonably well. On the road, it pulls strongly from 6k right up to 10k in the lower gears. Below 6k, it is decidedly lumpy, as though running rich.

My current theory is that the more restrictive ( in my opinion ) air filters have a similar affect to the partially closed choke, hence the improved performance over 6k rpm with the 98 mains, and that the rich running below 6k is due to the raised needles. Confirmed by sooty plugs after todays ride.

Next step is to revert to the 3rd slot on the needles. Trouble is, weather is closing in, fewer days left for these sort of tests. And of course, we are under lockdown, not that my solo rides around the local lanes have any implications for the NHS. Unless I ended up in Casualty ...
 
I'm getting psyched up to winterise the bikes. Got some Briggs and Stratton fuel stabiliser on the way. Drain the carbs, remove the batteries to the shed, for spells on the float chargers. A couple of bike covers arrived this afternoon, so two bikes will get a clean and a spray with some maintenance spray, then covered up until spring.

Once I've got these CL175 carbs sorted, ( I hope ! ) that'll also get put to bed. Maybe I'll then play with the SL175 alike if I get really bored ….
 
Finally !

Sorted at last. Revs to 9k and beyond in the gears, but still runs nicely at part throttle, picks up rather than bogs down, when blipping the throttle to change down. Idle when hot still isn't brilliant, but usable. Plugs turning toward tan colour, after giving it a sound thrashing this afternoon.

Carbs now back on standard setting of 38 pilots, 98 mains, needle in middle slot, all in another set of cleaned carb bodies. Running unmolested CB200 air boxes, with RamAir foam in place of paper. Just to be different, mounted on CB200 rubber manifolds. I was going to use my vacuum gauge with these, but as it seemed to be going OK, didn't bother.

And that'si till Spring. Winterised as last post and tucked up under a cover. It's the CB175s turn next ….
 
Good to hear it's sorted satisfactorily, just in time for the long nap so it will be ready to go next spring.
 
Middletons, don't want to hijack but have you ordered from jetsrus?? I am looking for original Keihin jets for my Honda cl100 105 and 110 mains. I have looked at Jetsrus web page and they indicate they have Keihin. Just wondering if you have actually purchased from them.

Thanks
 
I have ordered from them many times. You have to make SURE that you are ordering the correct jets, because I don’t believe they accept returns.
 
911hillclimber said:
Good to read!
what did you do to the carbs to find the sweet spot?
Click to expand...

This saga started with a poor idle on my CL175, fitted CL pipes and carbs on CL settings,92 main jets etc, running OK at full throttle.

I fitted my spare set of DS CB exhausts, and a freshly cleaned set of carbs, on CB settings as above. It didn't run well, I then proceeded change too many things at one go, until I came full circle back to CB settings and it runs OK. I think that the crucial thing was finding a set of floats and float valves that worked properly together. One of my initial problems was due to a leaking float, discovered by putting the float into hot water and watching the bubbles.
 
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